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/* Copyright (C) 1994 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
/* lockf is a simplified interface to fcntl's locking facilities. */
int
lockf (int fd, int cmd, off_t len)
{
struct flock fl;
switch (cmd)
{
case F_TEST:
/* Test the lock: return 0 if FD is unlocked or locked by this process;
return -1, set errno to EACCES, if another process holds the lock. */
if (fcntl (fd, F_GETLK, &fl) < 0)
return -1;
if (fl.l_type == F_UNLCK || fl.l_pid == getpid ())
return 0;
errno = EACCES;
return -1;
case F_ULOCK:
fl.l_type = F_UNLCK;
cmd = F_SETLK;
break;
case F_LOCK:
fl.l_type = F_WRLCK;
cmd = F_SETLKW;
break;
case F_TLOCK:
fl.l_type = F_WRLCK;
cmd = F_SETLK;
break;
default:
errno = EINVAL;
return -1;
}
/* lockf is always relative to the current file position. */
fl.l_whence = SEEK_CUR;
fl.l_start = 0;
fl.l_len = len;
return fcntl (fd, cmd, &fl);
}
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